Setting Guidelines; General - ABB RELION 670 SERIES Applications Manual

1MRK 506 369-UUS -
8.9.3
8.9.3.1
Line distance protection REL670 2.2 ANSI
Application manual
zone 1 settings, that is without selectivity conflicts. Careful fault calculations are
necessary to determine suitable settings and selection of proper scheme communication.
Fault resistance
The performance of distance protection for single phase-to-ground faults is very
important, because normally more than 70% of the faults on transmission lines are single
phase-to-ground faults. At these faults, the fault resistance is composed of three parts: arc
resistance, resistance of a tower construction, and tower-footing resistance.The resistance
is also depending on the presence of ground shield conductor at the top of the tower,
connecting tower-footing resistance in parallel. The arc resistance can be calculated
according to Warrington's formula:
×
28707 L
=
Rarc
1.4
I
EQUATION1456 V1 EN
where:
L represents the length of the arc (in meters). This equation applies for the distance protection zone 1.
Consider approximately three times arc foot spacing for the zone 2 and wind speed of approximately
30 m/h
I is the actual fault current in A.
In practice, the setting of fault resistance for both phase-to-groundRFPG and phase-to-
phase RFPP should be as high as possible without interfering with the load impedance in
order to obtain reliable fault detection.

Setting guidelines

General

The settings for Distance measuring zones, quadrilateral characteristic ((ZMRPDIS, 21)
are done in primary values. The instrument transformer ratio that has been set for the
analogue input module is used to automatically convert the measured secondary input
signals to primary values used in (ZMRPDIS, 21).
The following basics must be considered, depending on application, when doing the
setting calculations:
Section 8
Impedance protection
(Equation 251)
325